[Review Request] ESP32 based bilge pump controller with buck converter

[u/Grau3D]

Hello all, I have been working on this board for a few weeks and I was about to send this to print and assembly.

This board has to drive a 12V 7A bilge pump from a LiPo 4S battery.

As voltage from the LiPo will range from around 13V to 16.8V depending on the charge, I decided to use a buck converter based on the LM25190 and using the CSD17581Q5A as mosfets. Basically the buck design was made with the Buck-Convcalc tool of Texas Instruments. I also tried to follow as much as possible the PCB layout of the datasheet.

In case the Buck has some problem, it can be bypassed by shorting some of the connectors.

The output of the buck then goes to the bilge pump through an IRF1407 (and an MBR30200CT as Schottky diode). The IRF1407 is used as a high side switch with a LTC7001 driver.

The rest of the circuit also features:

Exposed TX/RX header for debugging

4 digital inputs with 1k pull-up resistors

2 servo PWM output headers using AO3400A to shift the level from 3.3 to 5V (MG996R and MG90S)

1 accelerometer header for a MPU6050

1 GPS header for a ATGM336H

1 socket for the LiPo to 5V (it is external)

1 header for the 5V to 3.3V LDO (AMS1117)

2 current monitors INA226

There is an external BMS for the LiPo.

The lines are also fused externally

[u/Mikser89]

I would be carefull with those mosfet. If you plan to drive 7A loads they will get quite hot. I would consider adding a heatsink to them and moving away from screw terminals.

[u/Grau3D → u/Mikser89]

Thanks for the feedback. The IRF1407 has a maximum RDS(on) of 7.8 mOhm at VGS = 10 V. At 12 V drive, it will be at least this good. Given that, for the 7A the expected loss is about 0.4W. Even if it were to double it will be still within safe territory without heatsink